The present invention relates to detecting vibration of a disc in a disc drive and more particularly to determining an operating speed at which user perceptible effects caused by such vibration emanating from the drive is reduced to a relatively less perceptible level.
Compacts discs or CDs, as they are often referred to, are used as a common form of economical storage media. Initially, CDs were used as a media for distributing music. Later CD-read-only-memory or CD-ROMs were used for distributing computer software. Today, with the advent of re-writable CD equipment into the consumer market and DVD (digital versatile disc) players, the CD has become a very popular media for storing audio, video and computer software.
With the growing popularity of CDs, the speed of rotation of CD drives has also increased from 1xc3x97 to 52xc3x97, and perhaps even faster speeds may be achieved going forward. A problem that has arisen due to the increasing speed of rotation of the CDs in a disc drive is a perceptible audio noise. The noise, for the most part, is caused by vibrations within the disc drive, and poses a source of concern and irritation to a user. A primary cause of the noise is warped and/or unbalanced discs, which may be the result of variations in the disc manufacturing processes and/or materials. Of course, when such warped and/or unbalanced discs are used at lower rotating speeds, as in the past, no perceptible noise results. Hence, the noise is brought about by the higher speeds of rotation, which in turn is necessitated by requirements for faster data rates.
European patent EP946940B1, by Siemens Nixdorf of Germany, discloses a CD ROM drive where in response to detecting noise or vibration in the drive, the speed of rotation of the CD is reduced. However this patent does not show an efficient method nor means for detecting the vibration. A PCT patent application WO990299 by Matsushita of Japan discloses attaching an accelerometer to the CD drive to detect vibration. A disadvantage of this method is the high cost of accelerometers, and in addition, there are concerns with space within the drive for mounting the accelerometer, and also concerns as to the location within the drive at which the accelerometer should be mounted.
Another approach is provided in JP11185369A2, by Hitachi Ltd. of Japan, which relates to using counterweights in a turntable in the CD drive to alleviate or offset the effects of an unbalanced or warped disc. Again, using such a turntable adds to the cost of the drive. U.S. Pat. No. 5,893,048, assigned to Dell USA, discloses a method of determining vibration of the CD by detecting the speed at which a read/write head in the CD drive moves, as the read/write head moves along an axis perpendicular to the CD, to maintain focus on a data track on the CD i.e. a focusing signal is monitored to provide an indication of the vibration of the rotating CD. This patent teaches rotating a disc at a high speed, and when the detected speed of movement of the read/write head is higher than an allowable limit, the speed of rotation of the disc is reduced to a lower speed. This method requires that a disc is rotated at a higher speed first, and at such speeds the CD drive will tend to emit a significant degree of audible noise caused by vibration. Consequently, a user will have to tolerate such noise until the detection and subsequent speed change occurs. Further, this patent teaches storing an identifier and corresponding vibration level of very disc that is loaded in the CD drive, and having a database to store such information. This means that a disc is tested only once and should the disc become warped or unbalanced later, the drive will not be able to detect the change and a user will have to tolerate any resultant noise.
The present invention therefore seeks to provide a method and apparatus for detecting vibration in a disc drive and an apparatus therefor, which overcomes, or at least alleviates, the above mentioned problems of the prior art.
In one aspect, the present invention provides a data storage drive for a removable data storage media having at least one data track thereon, wherein there is relative movement between the removable data storage media and a pickup head assembly, wherein the data storage drive has a tracking subsystem for maintaining alignment between the pickup head assembly and the at least one data track, the data storage drive comprising.
a vibration detect subsystem coupled to disable the tracking subsystem, and the vibration detect subsystem being coupled to receive at least one output signal from the pickup head assembly, wherein the at least one output signal is indicative of displacement of the pickup head assembly when the tracking subsystem is disabled.
In another aspect the present invention provides a data storage drive for a data storage media having at least one data track thereon, the data storage drive comprising:
a media mover having a speed control input for receiving a speed setting, and the media mover for removably mounting the data storage media thereto, for moving the data storage media in accordance with the speed setting;
a movable pickup head located proximal to the data storage media loaded on the media mover, the movable pickup head for reading and/or writing data to/from the at least one data track when the movable pickup head is substantially aligned with the at least one data track, the pickup head for detecting its relative position to the at least one data track and providing a tracking signal;
at least one actuator coupled the movable pickup, the at least one actuator having an input for receiving tracking information, and for locating the movable pickup head in accordance with the tracking information;
a vibration detector module coupled to the movable pickup head, and the vibration detector having an output for providing a pickup head displacement signal; and
a controller coupled to the media mover, the movable pickup head, the at least one actuator, and the vibration detector, the controller for receiving the tracking signal and the pickup head displacement signal, and providing the speed setting and tracking information, and the controller for inactivating the at least one actuator and measuring the pickup head displacement signal.
In yet another aspect the present invention provides a data storage drive for a removable data storage media having at least one data track thereon, the data storage drive comprising:
at least one control subsystem coupled to a movable pickup head assembly, a first actuator, a second actuator, and a speed controller, the at least one control subsystem for detecting the at least one data track and for moving the pickup head assembly to maintain focus on the at least one data track, for moving the pickup head assembly to maintain tracking between the pickup head assembly and the at least one data track, for monitoring data transfer between the pickup head assembly and the at least one data track, and for adjusting relative speed of movement between the pickup head assembly and the movable storage media to maintain reliable data transfer between the pickup head assembly and the at least one data track; and
at least another control subsystem coupled to the at least one control subsystem, the at least another control subsystem for disabling the tracking between the pickup head assembly and the at least one data track prior to detecting movement of the pick up head, for determining whether the movement of the pickup head is within at least one predetermined limit, and for changing relative speed of movement between the pickup head and the removable storage media to bring the movement of the pickup head within the at least one predetermined limit.
In still another aspect the present invention provides a method for detecting vibration in a read/write data storage drive for a removable data storage media, wherein the removable data storage media has at least one data track thereon, the method comprising the steps of:
a) initiating relative movement between a pickup head assembly, in the data storage drive, and the removable data storage media with tracking between the pickup head assembly and the at least one data track enabled;
b) setting the relative movement to resonant speed of the pickup head assembly;
c) when the relative movement is substantially at the resonant speed of the pickup head assembly, disabling the tracking;
d) measuring the displacement of the pickup head assembly with the tracking disabled to determine a vibration value; and
e) comparing the vibration value with a vibration value limit and changing the relative movement from the resonant speed to another speed in accordance with the result of the comparison.